Atherosclerosis (hardening of the arteries) is ten times more common in patients with SLE than in the general population. The purpose of this research study is to determine how frequently SLE patients have an abnormal heart scan, indicative of atherosclerosis. Research participants will undergo a nuclear medicine cardiac SPECT scan as an outpatient. The scan requires an injection of a small amount of radioactive tracer into an arm vein. The testing procedure requires a patient to be present for approximately 6 hours. If a patient weighs over 200 pounds, a second day of testing may be necessary. As part of the scan, patients exercise. Patients who have coronary heart disease (heart problems) might be at risk for angina (heart pain) or myocardial infarction (heart attack). No one with known heart disease will enter this study. The radiation exposure received from participating in this study is equivalent to an exposure of 3.4 rems to the whole body. Naturally occurring radiation (cosmic radiation, radon, etc ... ) produces whole body radiation exposures of about 0.3 rems per year. Occupationally exposed individuals are permitted to receive whole body exposures of 5 rems per year.